On 07/25/2007 07:15 PM, Robert Deaton wrote:
On 7/25/07, Rene Herman <[email protected]> wrote:
And there we go again -- off into blabber-land. Why does swap-prefetch
help updatedb? Or doesn't it? And if it doesn't, why should anyone
trust anything else someone who said it does says?
I don't think anyone has ever argued that swap-prefetch directly helps
the performance of updatedb in any way
People have argued (claimed, rather) that swap-prefetch helps their system
after updatedb has run -- you are doing so now.
however, I do recall people mentioning that updatedb, being a ram
intensive task, will often cause things to be swapped out while it runs
on say a nightly cronjob.
Problem spot no. 1.
RAM intensive? If I run updatedb here, it never grows itself beyond 2M. Yes,
two. I'm certainly willing to accept that me and my systems are possibly not
the reference but assuming I'm _very_ special hasn't done much for me either
in the past.
The thing updatedb does do, or at least has the potential to do, is fill
memory with cached inodes/dentries but Linux does not swap to make room for
caches. So why will updatedb "often cause things to be swapped out"?
[ snip ]
Swap prefetch, on the other hand, would have kicked in shortly after
updatedb finished, leaving the applications in swap for a speedy
recovery when the person comes back to their computer.
Problem spot no. 2.
If updatedb filled all of RAM with inodes/dentries, that RAM is now used
(ie, not free) and swap-prefetch wouldn't have anywhere to prefetch into so
would _not_ have kicked in.
So what's happening? If you sit down with a copy op "top" in one terminal
and updatedb in another, what does it show?
Rene.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
